Surface Wave Driven Air-Water Plasmas

The performance of a surface wave driven air-water plasma source operating at atmospheric pressure and 2.45 GHz has been analyzed. A 1D model has been developed in order to describe in detail the creation and loss processes of active species of interest and to provide a complete characterization of the axial structure of the source, including the discharge and the afterglow zones. The main electron creation channel was found to be the associative ionization process N$+$O$\to $NO$^{+}+$e. The NO(X) relative density in the afterglow plasma jet ranges from 1.2{\%} to 1.6{\%} depending on power and water percentage according to the model predictions and the measurements. Other types of species such as NO$_{2}$ and nitrous acid HNO$_{2}$ have also been detected by mass and FT-IR spectroscopy. Furthermore, high densities of O$_{2}$(a$^{1}\Delta_{\mathrm{g}})$ singlet delta oxygen molecules and OH radicals (1{\%} and 5 {\%}, respectively) can be achieved in the discharge zone. In the late afterglow the O$_{2}$(a$^{1}\Delta_{\mathrm{g}})$ density is about 0.1 {\%} of the total density. The plasma source has a flexible operation and potential for channeling the energy in ways that maximize the density of active species of interest.